The Democratic National Convention saw dramatic conflict between Mississippi's delegates and the rest of the convention. The group of delegates from Mississippi were from the Mississippi Freedom Democratic Party, whose delegates were sent to protest the Jim Crow primary that selected the official delegates of the state. Though this was against party rules, party leaders worked out a deal with the civil rights leaders, allowing two delegates from the Mississippi Freedom Democratic Party to remain. The rest of the state's delegates would be chosen according to party rules. Because of this, Johnson lost several southern states in the election, including Louisiana, Alabama, Mississippi, Georgia, South Carolina.
John F. Kennedy's brother, Robert F. Kennedy, had a personal conflict with Johnson, though he served as a member of his cabinet as Attorney General, and wanted to become his running mate. Johnson declined to choose Kennedy to be his running mate, instead choosing Hubert Humphrey, Senator of Minnesota.
The Republican candidates agreed to suspend their campaigns out of respect for John F. Kennedy after his assassination in November of 1963. They resumed their campaigns at the beginning of 1964. Frontrunners were conservative Senator Barry Goldwater of Arizona and New York Governor Nelson Rockefeller. Former Vice President Richard Nixon decided against running after his defeat in the previous election. Goldwater was the leader of the conservative faction of the Republican Party, and had done fairly well in the previous election's primaries. Rockefeller, on the other hand, was the leader of the liberal to moderate segment of the GOP. During his campaign, Rockefeller's reputation was marred by rumors of an extramarital affair, causing conservatives and female members of the Republican Party to end their support for him. When it became clear that Rockefeller could not win the nomination, his supporters switched to Pennsylvania Governor William Scranton, but it was too late for them to gain traction. Goldwater won the nomination, but was too conservative to compete in the general election.
Johnson's campaign portrayed Goldwater as an extreme conservative who fought against civil rights, and who wanted to get rid Johnson's of social welfare programs. The Democrats used the fear of nuclear war to motivate antiwar voters to vote for the Democratic candidate, showing Goldwater as eager to go to war.
The election of 1964 was the first election in which the District of Columbia was able to vote in a presidential election, after the ratification of the Twenty-third Amendment to the U.S. Constitution. The total number of electoral votes available was 538, which is still the total today.
The 1964 election resulted in a landslide victory for Johnson, winning forty-four states and over 61 percent of the popular vote. Johnson broke the record for the highest number of electoral votes received by a candidate with 486 (FDR previously held the record with 472 electoral votes). The election of 1964 also saw the beginning of the shift of southern states from being Democratic to being Republican states, which has increased over time. This election also marked the shift of New England from Republican to Democratic.